Agitator or mixing tanks with rotating agitator apparatus are typically used to mix chemical compounds. Frequently, the ingredients being mixed in the agitator tanks require a sterile environment, such as when ingredients are being mixed to prepare a pharmaceutical product. Although some applications do not require a sterile environment, the United States Food and Drug Administration has set out strict sterile requirements for some solutions. To provide such a sterile environment, mixing tanks must be constructed to prevent contaminants from entering the tank during the entire batch process, including filling the tank, mixing and draining the tank.
The use of magnetic drives for driving the agitator apparatus has been known for a long time, since such drives do not require a physical connection or seals between moving parts of the drive means and the agitator apparatus in the sterile environment. In agitator tanks adapted for magnetically driven agitator apparatus, the agitator apparatus within the tank includes a magnetic element near the bottom of the agitator tank, which is engaged by a corresponding magnetic element on a drive motor positioned outside the tank. Activation of the drive motor having the corresponding magnetic element positioned adjacent the magnetic element of the agitator apparatus causes the agitator apparatus to rotate within the agitator tank.
Even more recently, sterile agitator tanks have been developed that utilize a flexible vessel as the mixing container. The flexible vessels can be constructed in a sterile environment and sealed prior to use. Such systems, which use a tank support to maintain the integrity of the flexible container when filled, generally are disposed of after use, to obviate the need for cleaning so as to recreate a sterile environment in the vessel between uses. Thus, the ability to control the sterile environment is greatly improved.
Additionally, agitator tanks for use in sterile applications are known to include the agitator apparatus within the sealed vessel when shipped. In these agitator tanks, the sterile agitator apparatus is placed within the sterile vessel prior to sealing, minimizing the potential for breaching the sterile environment.
Examples of agitator tanks with magnetically driven internal fluid agitating apparatus include U.S. Pat. Nos. 4,209,259; 4,993,841; and 5,470,152, Japanese Patent No. JP 56-045752 and Published PCT Application No. PCT/US02/31478. Each of these references describes agitator tanks with agitating apparatus having driven magnetic elements that are engaged by adjacent cooperating drive magnetic elements associated with a drive means.
Of the references cited, U.S. Pat. No. 5,470,152 describes an agitator tank with a drive housing into which the drive magnet is inserted. An impeller having a magnetic element is attached to the drive housing with the magnetic element having magnets oriented vertically, so that the magnets are parallel with the longitudinal axis of the drive housing containing the cooperating magnetic element of the drive motor. As shown and described in the reference, the impeller is removably attached to the bottom portion of the drive housing with a clip.
U.S. Pat. Nos. 4,209,259 and 4,993,841 describe mixing vessels with magnetically driven agitator apparatus, in the form of impellers mounted on posts in the vessels. Each of these references describe the agitator apparatus as located within the vessel in an area related to a flange or recess that positions the impeller with respect to the drive means. However, the impellers of these references merely reside in the vessel at a single location on a post, and can be removed by pulling on a ring on the terminal end of the agitator apparatus.
Similarly, the device of PCT Application No. PCT/US02/31478 utilizes an impeller that is received by a post located on a rigid portion of the mixing vessel. The remaining portion of the mixing vessel is called out as being a flexible portion, described in the reference as a bag. The impeller has a magnetic element that is driven by an external drive motor having a magnetic drive element.
Japanese Patent No. JP 56-045752 is directed to a magnetically driven stirring device having a rotating circular plate on ball bearings fixed to the bottom of the vessel, where the magnetic element of the agitator apparatus is associated with the bottom of the vessel. The agitator apparatus of this reference is formed of a metal alloy for wear purposes.
None of the prior art references, however, describes a method of mixing using a sterile sealed single use mixing vessel including a centrally disposed shaft, attached to the top and bottom portions of the vessel and utilizing radial or thrust bearings, such as slide bearings, ball bearings, journal bearings, or roller bearings, to facilitate rotation of the shaft, on which one or more impellers are mounted. Moreover, none of the references describes mixing in a single use mixing vessel having a drain port incorporated into the bottom shaft attachment member for draining the vessel once the mixing process has been completed.
Furthermore, none of the prior art references describes a method of mixing using a sterile sealed single use mixing vessel comprising a flexible bag including a centrally disposed shaft, which is attached to the top and bottom portions of the vessel, has one or more impellers, is foldable or may be assembled from sections, whereby the impeller(s) are positioned at a predetermined level. Assembling the centrally disposed shaft may be accomplished from the outside of the mixing vessel by a manual manipulation of the user.